Field of the Invention
The present invention relates to a zoom lens, which is suitable for, for example, an image pickup optical system used in an image pickup apparatus such as a digital still camera, a video camera, a monitoring camera, a broadcasting camera, a silver-halide film camera, or the like.
Description of the Related Art
In recent years, in an image pickup apparatus using a solid-state image pickup element, the solid-state image pickup element is increased in size, which accompanies increased functionality of the image pickup apparatus or downsizing of the entire apparatus. Then, as an image pickup optical system used with the image pickup apparatus, a zoom lens that is bright and has a wide angle of view at a wide-angle end, a high zoom ratio, and high optical performance over an entire zoom range has been sought for. As a zoom lens satisfying those demands, there is known a five-unit zoom lens including, in order from an object side to an image side, first to fifth lens units respectively having positive, negative, positive, negative, and positive refractive powers.
In Japanese Patent Application Laid-Open No. 2007-264174, there is disclosed a zoom lens in which a first lens unit to a third lens unit, and a fifth lens unit are configured to move during zooming, and which has a zoom ratio of about 10. In Japanese Patent Application Laid-Open No. 2013-117667, there is disclosed a zoom lens in which lens units are configured to move during zooming, in which a fourth lens unit is configured to move during focusing, and which has a zoom ratio of about 5.
With the five-unit zoom lens having the above-mentioned refractive power arrangement, it is relatively easy to downsize the zoom lens, to realize a large aperture ratio, the wide angle of view, and the high zoom ratio, and to obtain the high optical performance. However, when a focal length at a telephoto end is to be increased to further increase the zoom ratio while realizing the large aperture ratio, various aberrations such as spherical aberration, astigmatism, and chromatic aberration are increased, and hence it is difficult to maintain the high optical performance. In particular, when an f-number is to be reduced for brightness, the occurrence of the various aberrations such as the spherical aberration and coma is increased at the telephoto end. Moreover, when the angle of view is to be increased, the occurrence of the various aberrations such as the astigmatism and lateral chromatic aberration is increased at the wide-angle end, and a front lens diameter is increased.
In the five-unit zoom lens, in order to downsize the zoom lens, to realize the large aperture ratio, the wide angle of view, and the high zoom ratio, and to obtain the high optical performance over the entire zoom range, refractive powers and lens configurations of the lens units are appropriately set. In addition, it is important to appropriately set movement conditions and the like of the lens units accompanying zooming.